linux-kernel - Re: [PATCH] Don't mlock guardpage if the stack is growing up

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Message-ID: <BANLkTi=4raxPiRzBH=b44=SLsAujhx2xUw@mail.gmail.com>
Date:	Wed, 11 May 2011 19:12:57 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Milan Broz <mbroz@...hat.com>
Cc:	Alasdair G Kergon <agk@...hat.com>,
	Matthew Wilcox <matthew@....cx>,
	Zdenek Kabelac <zkabelac@...hat.com>,
	Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz>,
	linux-kernel@...r.kernel.org, linux-parisc@...r.kernel.org,
	Hugh Dickins <hughd@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH] Don't mlock guardpage if the stack is growing up

On Wed, May 11, 2011 at 1:42 AM, Milan Broz <mbroz@...hat.com> wrote:
>
> Another one is cryptsetup [..]

Quite frankly, all security-related uses should always be happy about
a "MCL_SPARSE" model, since there is no point in ever bringing in
pages that haven't been used. The whole (and only) point of
mlock[all]() for them is the "avoid to push to disk" issue.

I do wonder if we really should ever do the page-in at all. We might
simply be better off always just saying "we'll lock pages you've
touched, that's it".

                       Linus
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